The present invention relates to a device for mechanically stripping electrical and fiber-optic single- or multi-line conductors or wires and cables. The device comprises: an inlet opening for the conductor or for a conductor end, a clamping device having at least one clamping jaw and at least one knife for cutting through an insulation and a drive for radial incision and axial withdrawal of the knife.
Stripping devices which use one pneumatic actuation cylinder each for the clamping jaws and knife actuation have been offered. These are bulky, which presents problems, for example, when processing complicated cable trees.
An early further development likewise comprised two cylinders. One cylinder served for driving the clamping jaws and for axial driving of the knives for the stripping movement. The second drive served for closing the knives. It travels concomitantly on a stripping carriage. This development was launched on the market by a predecessor of the Applicant, under the name AM2. In this design, a carefully thought out mechanism ensured that, when the stripping force was increased, the clamping force at the clamping jaws was automatically increased. This mechanism or its principle in particular was later also copied by others.
A stripping device further improved compared with the prior art described above was designed by the Applicant as early as 1982 and produced from 1986 onward and was launched on the market under the name US 2015. US 2500 and US 2045 are further developments of US 2015 by the Applicant.
These mechanical, pneumatic stripping devices now form the accepted prior art worldwide for small light stripping devices having non-rotating knives and are therefore frequently copied.
They have a high stripping force and cycle rate and are compact and convenient. They furthermore avoid the jamming of stripping residues by means of blowing out with air and drawing back of a conductor stop.
They have a single flying pneumatic cylinder which serves both as a drive for the knives and as a drive for the clamping jaws. The stripping axis (or stripping plane) in which the stripping forces act directly (this is parallel and, depending on the design and on the arrangement of the knife holders, parallel to the (US 2015) and sometimes virtually in the cable axis (US 2500)) is positioned adjacent to and parallel to a control axis (or control plane or control mechanism) around which axis (or in which plane or in which mechanism) is arranged a control rod which carries control elements for actuating the clamping jaws and knife jaws. The drive axis for applying the stripping and control forces (this is virtually the axis of the pneumatic cylinder) lies in the control axis. The result is therefore a specific construction length, since both drive elements and control elements are arranged along this drive axis. Since the drive axis and the stripping axis are parallel but do not coincide with one another, the resultxe2x80x94depending on the stripping forcesxe2x80x94is tilting moments which have to be absorbed by the bearing. However, the absorption of these tilting moments is associated with loss of drive energy.
A length adjustment stop for the conductor is drawn back during stripping of the insulation so that jamming cannot occur.
Disadvantageously, however, all these known devices require a pneumatic fluid and corresponding fluid feed means for operation. For example, in the DIY area and on building sites, this gives rise to problems (compressor for pneumatic fluid).
Attempts are being made worldwide to modify the design of a US 2015 or a comparable device in such a way that it is possible to dispense with the pneumatic fluid. Electrical drives have been used.
The A1 01 of Zollern+Frxc3x6hlich uses, as a drive principle, an electric motor which drives various cam disks for clamping, cutting into and stripping the insulation: Apart from a bulky design and complicated force transmissions, the stripping cycle in this machine is too slow compared with a US 2015. U.S. Pat. No. 4,327,609 also describes an embodiment having an electric motor and cam disks.
The W-2020 from Yoshiki likewise has an electrical drive motor and various transverse drive elements, which however make the design too bulky compared with a US 2500.
A more recent design of Cosmic KK, which is described in JP-10-112913 A, corresponds in the mechanical part to the mechanical design of US 2015, the pneumatic cylinder being replaced by a laterally located electric motor with spindle drive and gear. The abovementioned disadvantage of resultant tilting moments between drive axis and stripping axis was not avoided since, here too, the drive axis coincides with the control axis. In addition, it is substantially larger than the US 2015, but the stripping cycle is substantially slower owing to poor dynamics. A laterally located electric motor drives an axially floating spindle with a ballscrew nut by means of a toothed-belt gear and a spline shaft. Provided coaxially with the spindle are two conical surfaces as control surfaces for a clamping device and for a knife drive analogously to US 2015, which are thus driven as if by a piston rod with combs.
Apart from the poor compactness and slow stripping cycle, this known design thus furthermore has the disadvantage of relatively large, complicated control surfaces which, because drive axis and control axis coincide, include the spindles in them and must be mounted thereon, which can lead to additional frictional losses during the rotation of the spindle. Since the stripping setup (knives, knife jaws, feed pipes) which is arranged around the stripping axis and is axially displaceable by the spindle generates high axial forces, the relatively large distance between the stripping axis and the axis of the spindle results in the above-mentioned relatively large tilting moments and therefore in further force losses and frictional losses. Further losses of axial shear force arise through friction in the spline shaft coupling.
The document EP-A-0352038 describes a device for stripping conductors along a stripping axis, comprising at least one each of an incision, stripping and control mechanism with at least one control element on the control mechanism. This known device is designed in such a way that the control mechanism is separated from the drive axis, and that the drive axis is parallel to the stripping axis. However, this design requires a separate drive for each axis, so that it is large and bulky and must have suitable electronics for coordinating the motors.
One of the objects of the present invention is thus to provide an improved stripping device whose construction length is shorter than a theoretical construction length in the case of structures having integrated drive axis and control axis. In a further step, this drive energy should be optimally utilized and hence above-mentioned losses very substantially avoided. Nevertheless, it should as far as possible be as compact as US 2015 or US 2500.
In a development step independent thereof per se, the pneumatic drive as known per se should be capable of being driven rotationally, in particular by means of electric energy, and the disadvantages mentioned in this context should be avoided.
The design should manage with a single drive motor, as in the case of said US machines.
According to the invention, the control mechanism of the drive axis is arranged separately. In this case, surprisingly, the construction length can be reduced by eliminating integration. The separation of the drive axis and control axis also results in a reduction in the construction length since only control elements, but no couplings or the like for the drive shaft (piston rod, spindle or the like) need be provided along the control axis.
An improved further development envisages that the drive axis is parallel between the stripping axis and the control mechanism. In the context of the invention, the control mechanism optionally also comprises a brake which assists with the control and accordingly can also generate tilting moments. Preferably, distances between drive axis and stripping axis and between drive axis and control axis are chosen so that any tilting moments between these axes build up symmetricallyxe2x80x94but with opposite moment directionxe2x80x94around the drive axis, so that these tilting moments reduce one another and the corresponding loads on the bearings are reduced. This leads to the saving of drive energy; i.e. greater stripping forces can be applied with the same drive energy. However, this furthermore means that the stripping device can be designed as a whole to be smaller, which in many cases is a requirement of the users.
The xe2x80x9caxesxe2x80x9d mentioned in this Application are not necessarily axles in the mechanical engineering sense. Rather, they correspond to mathematical or spatial axes or directions or planes. They need not necessarily be absolutely linear and absolutely parallel. Rather, they have approximate relationships with one another whichxe2x80x94comprehensible to those skilled in the artxe2x80x94are given by the teaching according to the invention with regard to shortening of design and torque compensation. The embodiments presented in the following description have, as a further axis, also a cable axis or a plane in which the cable lies. For the purposes of the invention, this axis or plane may be separated from the stripping axis or stripping plane or may coincide with it, as, for example, in the known model US 2500.
Since the stripping forces as a rule are larger than the control forces for clamping and/or cutting into a cable, the drive axis will in principle preferably be positioned in the vicinity of the stripping axis.
This effect according to the invention is independent of the choice of the drive motor. Instead of a pneumatic cylinder, linear electric motors or rotary motors having spindles may be used.
In an independent but preferred step, the known pneumatic cylinder is replaced by a rotary motor, preferably by an electric motor, whose drive shaft is connected by means of a coupling or by means of a force transmitter to a threaded spindle, which in turn moves control surfaces both for the clamping jaws and for the knife, a coupling being arranged between at least one of the driven components and the motor. This was unknown to date in the case of stripping machines having an electric motor.
An alternative development with axially displaceable mounting of the motor and a spindle device rigidly connected axially therewith has the advantage of being capable of being constructed even shorter, which might be an advantage for portable devices.
Known electrically actuatable stripping devices, such as, for example, the HC 207 (1985) of the Applicant (cf. U.S. Pat. No. 4,745,828), require separate drives for actuating the knife and the clamping device. There, the clamping device was actuated by an attracting magnet while knife jaws and centering jaws were driven by means of a spindle with conical control surfaces. A further drive rotates the knives additionally about the cable axis. A plurality of drives increase the construction volume on the one hand and the control costs on the other hand.
A coupling provided according to the invention and/or a corresponding force transmitter or the axial release of the motor, however, permits free running of any affected control surfaces, in order to be able to carry out various stripping steps or stripping movements, such as closing of clamping jaws and closing of knives and in particular the axial stripping, in succession. The simplest coupling used is a spline shaft on the motor output shaft with coupling sleeve on the spindle, or vice versa. An alternative to this would be to provide a carriage which carries the motor next to the spindle and the spline shaft, so that the spindle with the motor can move at any rate axially relative to the housing. In both cases, the spindle and the control surfaces are displaceable axially and relative to the housing.
A preferred further development envisages load-dependent control of the coupling. Such an automatic control is realizedxe2x80x94optionally in a plurality of partsxe2x80x94for examplexe2x80x94and in the manner known per sexe2x80x94by means of a spring and/or brake.
According to a preferred embodiment, the coupling comprises a threaded nut, in particular for friction-reducing reasons a ballscrew nut, which is driven by the threaded spindle. In embodiments with a continuous spindle, preferably all nuts running thereon are in the form of ballscrew nuts.
Within the scope of the invention, the spindle devices comprise various groups of spindles:
A) with a coupling to the motor;
a spindle having a continuous thread, as known per se. In the case of the division according to the invention of the drive and control axes, it is advantageous compared with the prior art;
a spindle having two thread sections (main and secondary thread sections) with different thread pitches permits actuation of the clamping jaws and stripping knife on the basis of force/speed division and moreover replaces a gear;
B) as for A), but the spindle is rigidly connected to the motor and in turn the motor is axially displaceable relative to the chassis, resulting in an even shorter design;
C) spindle connected to the motor via a spindle nut: A spindle having two separate thread sections with opposite thread directions with the same thread pitch leads to advantageous driving of the controlled components, particularly good utilization of the driving energy additionally being permitted in the case of different thread pitches;
D) a main spindle rigidly connected to the motor;
a secondary spindle which is connected to the main spindle via a spindle nut optimizes the advantages of the latter design in that the smaller moment of inertia of a threaded spindle in a spindle nut has further advantages in terms of the dynamics
All variations, with the exception of the first one under A), are by themselves novel and inventive in the application for stripping drives.
A stripping device which is thus special and has at least one clamping jaw and at least one stripping knife and has an electrical drive via a two-part threaded spindle.
As a particular advantage of the design, said design automatically adapts the clamping force in the entire stripping region, like the abovementioned pneumatic devices. Moreover, it has the advantage that, with an appropriate pitch design, it permits a different pitch and hence different forces and speeds for the different operations.
The invention relates to a preferred solution in which the spindle is divided into two, a main spindle and a secondary spindle, the two parts being connected to one another via a spindle nut. This replaces a spline shaft which is connected to the drive and also achieves undesirable frictional losses per se. The spindle nut arrangement results in particularly advantageous movement sequences: during start-up, there is immediately an axial thrust on the spindle nut, which thus exerts an axial thrust so that the required braking force for the movement sequence can be reduced.
The designs of the invention may be formed in contrast to a preferred division of the drive and control axes, but also according to the known design with coinciding control and drive axes, in which they still have advantages over the known one.
According to a particular embodiment of the invention, the motor is in the form of a coreless direct current motor. This accelerates the dynamics and the fast speed reversal which occurs in the course of an operating cycle.
A particularly further developed design, comprising an ejector, furthermore has the advantage of actively ejecting insulation residues. It is subjected to only little bending load, which increases its life. Preferably, that end of the ejector according to the invention which faces away from the knife runs at least partly concentrically around the rotary shaft coordinated in each case with the respective knife jaw. The invention also covers a preferred further development of the ejectors.
A preferred device uses a direct current motor whose reversal of the direction of rotation is triggered by electrical position sensors. Preferably, the output shaft and the spindle are aligned because this minimizes the construction width of the stripping device. An electronic control can be arranged below or above the motor without increasing the construction width. According to a particular embodiment of the electronics, these canxe2x80x94as known per se in the case of continuous cable processing machines (e.g. CS 9100 of the Applicant)xe2x80x94take place automatically according to a program, in order to strip different cable dimensions in succession. Any possibilities for setting dimensions would also be automated for such a design.
The device according to the invention is thus also suitable for a portable hand-held device which can be optimally used in particular also for cable tree processing.
In addition to the preferred electric motors, fluidic rotary motors or other rotary drives can also alternatively be used.